Alcohol concentration testing using saliva and the breath has been shown to be highly correlated to alcohol concentration testing using blood, which is the gold standard of alcohol concentration testing. Alcohol testing using blood, saliva, and breath has proven extremely predictable and reliable, especially when determining current intoxication.
However, using urine alcohol concentrations as the basis for alcohol testing has been shown to be measurably less reliable. This is especially true when attempting to determine a person’s intoxication at the time of testing, which is the aim of most testing applications. Here are a few reasons why:
Since a person has the ability to choose the frequency of urine evacuation (if at all), along with the amount of evacuation, this has a significant impact on urine alcohol levels in the bladder. For example: A test subject drinks 6 beers in 2 hours then stops drinking. A breath test given 2 hours after he stopped drinking would only show negligible blood alcohol levels. However, if that same test subject was also given a urine test 2 hours after he had stopped drinking, his urine alcohol levels would be extremely high if he had not evacuated his bladder prior to the urine test, even though he was technically sober.
Furthermore, test subjects who have certain conditions such as urinary tract infections with a fermenting organism like Candida Albicans, or diabetes (which causes glucose to leak into the urine)may produce a positive test for alcohol based on a urine sample, even though the test subjects consumed no alcohol.
Alcohol testing using breath and saliva methods is also able to produce immediate test results. However, because urine alcohol testing generally requires onsite collection and the need to ship the collected specimen to an independent laboratory for confirmation testing, this method can take days to obtain results.
In addition to predictability issues, the costs to purchase, collect, and obtain laboratory confirmation results for urine alcohol testing can be relatively expensive when compared with more reliable testing methods using saliva and breath.
Update to article 12/2018: In the last 2-years, instant urine EtG tests have been made available. However they are only allowed for forensic use only applications (typically court-ordered abstinence enforcement programs), and are not appropriate for workplace testing programs. These instant tests are cost-effective and very reliable and have cutoff levels of 500 ng/mL. The instant EtG alcohol test offered by AlcoPro provides the longest window of detection for alcohol of any test method available…up to 80 hours after consumption.